Biophysical studies of macromolecules

Abstract

Hydrodynamic theories of macromolecular structure have been critically examined and used in the experimental study of the conformation of various biological molecules. This work has been carried out giving careful consideration to ancient and modern wisdom. The fundamental molecular structure of liver glycogen has been investigated using a variety of biophysical techniques, including intensity fluctuation spectroscopy. It has been found that above a certain minimum size, molecules of this material are hydrodynamically equivalent to one another, and behave as if comprised of ideal spherical subunits. Smaller molecules do not have a smooth hydrodynamic surface and display a much higher degree of frictional interaction with the aqueous solvent. It has also been shown that when treated with disulphide-bond breaking reagents, large glycogen molecules are disrupted, but the structure of the subunits is undisturbed. The role of protein in glycogen structure has been confirmed by these studies. Intensity fluctuation spectroscopy has also been applied to the study of protein conformation. The frictional coefficients of bovine serum albumin monomers and dimers have been measured, and an apparent conformational change in the monomer detected upon the binding of salicylate. The unfolding and subsequent aggregation of lysozyme when it is thermally denatured have been observed and the hydrodynamic radii of the native, folded state and the expanded, unfolded state of protein have been measured. There is a well defined transition temperature for the denaturation process.